Polymers are having increased use in microelectronic applications. Polymers are used in multi-level structures as a dielectric layer between layers containing patterned electrical conductors. These multi-level structures can be used as a substrate on which an electronic device, for example, a semi-conductor chip, can be electrically mounted. These multi-level structures can also be used as the top electrical conductor wiring levels of a ceramic substrate on which an electronic device is electrically mounted. These multi-level structures can also be used as the top electrically conductive layers of an electronic device, for example, a semiconductor chip.
The multi-layer polymer electrical conductor structure is fabricated by forming a first polymer layer on which an electrical conductor pattern is formed. A second polymer layer is disposed over the electrical conductor pattern. The second polymer layer has electrically conductive through-holes for electrical connection to the conductor pattern on the first polymer layer. A second electrically conductive pattern is disposed on the second polymer layer. Electrically conductive through-holes electrically interconnect electrically conductive pattern on the first polymer layer with the electrically conductive pattern on the second polymer layer. A structure having any number of electrically conductive layers and polymer layers can be fabricated by repeating these steps.
One of the problems in fabricating a multi-level polymer structure is to get adjacent polymer layers to adhere to each other. An adhesive layer can be disposed between adjacent polymer layers. However, adhesives have been found generally incapable of withstanding subsequent heat treatments fabricating a multi-level polymer metal structure for microelectronic applications. The adhesives as a result of these heat treatments degrade resulting in the delamination of adjacent polymer layers.
IBM Technical Disclosure Bulletin, Vol. 22, No. 1, June, 1979, p. 42, entitled "Method for Improving Adhesion of Polyimides" describes treating a cured layer of polyimide to a tetra-alkyl ammonium hydroxide salt and a dilute aqueous solution of acetic acid. A layer of uncured polyimide is deposited on the treated surface and then cured to a polyimide layer. A chemical bond is believed to be formed between the two polyimide layers, thereby increasing the adhesion between the layers. Use of a hydroxide salt has the disadvantage of introducing ions between the polyimide layers. These ions are contaminants which can result in low level current flowing between otherwise electrically isolated electrical conductors which are disposed between the polyimide layers.
An invention herein is treating a polymer surface with a water vapor plasma to enhance the adhesion of the treated layer to a second polymer layer.
U.S. Pat. No. 4,382,101 describes enhancing the adhesion of a metal layer to a polymer layer, e.g. a polyimide layer, by treating the surface to a plasma of a gas such as helium, argon and combinations of gases such as carbon tetrafluoride in oxygen.
U.S. Pat. No. 4,765,860 describes enhancing the adhesion of a metal layer to a polymer layer e.g. a polyimide layer, by exposing the polymer layer to a low temperature plasma of one or more of helium, neon, argon, nitrogen, oxygen, air, nitrous oxide, nitrogen monoxide, nitrogen dioxide, carbon monoxide, carbon dioxide, bromine cyanide, sulfur dioxide, hydrogen sulfide and the like.
U.S. Pat. No. 4,755,424 describes enhancing the adhesion of a metal layer to a polymer layer having minute projections thereon by subjecting the polymer surface to a corona discharge.
U.S. Pat. No. 4,740,282 describes a treatment for a synthetic plastic intraocular lense to avoid protein adhesion to the lens. The lens is treated by first cross-linking the lens surface by treating the surface with a stream of low pressure hydrogen gas in the presence of an A.C. electrical discharge, and thereafter treating the cross-linked surface with hydroxyl radicals to hydrophilize the surface.
The article in the Journal of the Chemical Society of Japan, No. 11, 1987, p. 1995, entitled "Effect of H.sub.2 O Plasma Treatment on the Adhesion of Metal Thin Films" of Nakamae et al., describes the treatment of poly(ethylene terephthalate) films with a H.sub.2 O plasma which improves film wettability and the adherence of a Co film deposited onto the polymer film.
The article in Fresenius Z. Anal. Chem. (1984) 319; p. 841-844, entitled "Angle Resolved ESCA Analysis of Plasma Modified Polysterene", to Evans et al. describes Angle Resolved ESCA studies of polysterene surfaces treated with H.sub.2 O plasma. The studies showed higher concentrations of carbonate and ester linkages as compared to O.sub.2 plasma treatment.
The article in the Journal Polymer, August 1980, Vol. 21, p. 805, entitled "Surface Modification of Poly (ethylene terephthalate) by Electrical Discharge Treatment" describes treating a film of poly (ethylene terephthalate) to an electrical discharge. Treatment enhanced the autoadhesion between two sheets of the film.
The article in the Journal of Macromolecules 1984, 17, pp. 1013-1019, entitled "Preparation and Characterization of Functionalized Polyethylene Surfaces" to Nuzzo et al. describes treating a polyethylene film to an oxygen, water or hydrogen gas plasma and the analysis of the treated surface with a high resolution x-ray photoelectron spectroscopic analysis.
The article in the Journal Vide Couches Mines (France) No. 237, Suppl.--1987, p. 53-55 entitled "Polymer Surface Treatment by an Argon-Oxygen Microwave Discharge" to Darchicourt et al. describes treating a polymer surface to an argon-oxygen microwave discharge.
The article in the Journal of Materials Research submitted May, 1986 entitled "Multitechnique Surface Spectroscopic Studies of Plasma Modified Polymers" to Hook et al. describes treating a polymethylmethacrylate film with a RF-plasma glow discharge created from a Ar/H.sub.2 O gas mixture which incorporates high concentration of hydroxyl groups on the polymer film surface.
The cited art does not teach or suggest alone or in combination treating a polymer surface with a water vapor plasma to enhance the adhesion of the first and second polymer layer.
It is an object of this invention to promote the adhesion of a first polymer surface to a second polymer surface by treating at least one polymer surface with a water vapor plasma.
It is another object of this invention to promote the adhesion of a polyimide polymer surface to a second polyimide polymer surface by treatment of the polyimide surface with a water vapor plasma.